In photometry and colorimetry, standard CIE illuminant A tungsten-filament light sources have exclusively been used as calibration standard sources since 1932.
As LEDs increasingly replace traditional lighting new means and methods of calibration are
needed due to differences in emission spectra.
Technical Report CIE 251:2023, just published in February 2023, presents a LED reference spectrum titled “CIE Reference Spectrum L41”.
The shape of this spectrum is based on available LED illuminants as well as minimum error considerations in terms of spectral mismatch errors of photometers. However, it was not designed to match an existing LED on the market. The intention is to use this source in addition to standard CIE Illuminant A for photometer calibration, especially for LED measurements. The report also contains information about typical magnitudes of spectral mismatch errors with V(λ)-filtered photometers in measurements of LEDs as well as other types of light sources. This is based on the assumption that CIE reference spectrum L41 is used for photometer calibration instead of CIE standard illuminant A. Finally, the document introduces a quality metric for selection of white LEDs as physical LED standard sources.
On this basis, Gigahertz-Optik developed the LED-based standard BN-LLSF-2P which is perfectly suited for photometric calibrations according to CIE 251:2023 (see spectra comparison with CIE reference spectrum L41 below). The source matches the reference spectrum very well with just minor deviations as indicated by the spectral distribution mismatch index of fsf, L41=0.016. The standard can be used both as an illuminance calibration standard for photometers as well as a luminous flux standard in combination with an integrating sphere in 2π geometry.
The BN-LLSF-2P standard is offered together with calibration by Gigahertz-Optik’s ISO 17025-accredited calibration laboratory to guarantee the highest quality and standards.
Contact us today to discuss your application and pricing info-us@gigahertz-optik.com
